1. Field of the Invention
This invention relates to an image sensing apparatus which permits white balance setting with ease.
2. Description of the Prior Art
Heretofore, operators of image sensing devices, such as video cameras, have obtained a white balance, after turning on a power supply switch, by pushing a white balance switch while directing the camera lens toward a white wall or the like.
Meanwhile, various image sensing devices of the kind adapted to take still pictures have been developed over recent years. It is important for devices of this kind to achieve a stand-by state as promptly as possible after the power supply is switched on in order to take advantage of opportunities to take pictures. However, conventional video cameras have been too poorly designed to meet this requirement.
There is another disadvantage to the conventional video camera. When the power supply is on, an automatic light quantity control (ACL) circuit performs a servo control operation on the aperture of an iris to control the light quantity incident on the image sensor. However, in sensing light from an object having a broad dynamic range, the output of the image sensor, for example, becomes saturated and a correct white balance adjustment is not possible.
Moreover, it would be advantageous to have an image sensor which could be used with presently available lenses for existing cameras using silver halide film.